The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Electronic devices, including consumer electronic devices, appliances, and the like, often include a switching device such as a push-button keyboard input device. The keyboard may include electrical switches connected to a series of resistors and an input voltage. Depression of a keyboard push-button or “key” may close one of the switches, thereby generating an analog output voltage. The analog output voltage may be a fraction of the input voltage, depending on the configuration of the switches and resistors. An analog-to-digital converter may convert the analog output voltage to a digital output that corresponds to the depressed key.
Traditionally, switching devices are biased either at the input voltage or at the circuit's ground. Thus, when no keys are pressed, the output of the switching device is either the input voltage or zero volts. When a push-button is pressed, a switch is closed causing an output between zero volts and the input voltage. Control and response circuitry may receive the output and recognize the output voltage as corresponding to the pressed key. The control and response circuitry may include and analog-to-digital converter and/or a control module for controlling a controlled device in response to the voltage output.
Push-buttons, or keyboard keys, may become stuck. In the traditional system, the switching device becomes inoperable when a key is stuck as the output of the switching device also becomes stuck. Pressing another key of the keyboard may cause the switching device to output an analog output voltage that does not correspond to either the pressed key or the stuck key.
Such a switching device may be implemented on an integrated circuit board (IC). The IC hosting the switching device may also host a user display, such as an LED display or an LCD panel. Control and/or response circuitry for the electronic device may be hosted on a separate IC electrically connected to the IC that is hosting the user input switching device and user display.
During use of the electronic device, the two IC's may become disconnected. In the traditional system, the control circuitry is not able to detect the malfunction. When the two IC's are disconnected, the analog output voltage may simply be zero volts or the input voltage, and the control circuitry may simply read the analog output voltage as having received no user input. Thus, the control and/or response circuitry may simply proceed as if no user input has been received and no key has been depressed. In such case, the user is not able to input key presses to the control circuitry to pause operation of the controlled device or to shut down or power-off the controlled device.